The present invention relates to an endoscope having a suction selector mechanism for opening/closing a suction channel.
A conventional suction selector mechanism of an endoscope is shown in FIGS. 1 and 2, in which a cylindrical piston 2 is slidably fitted in a cylinder 1. An opening 4 communicating with the channel defined by a suction channel member 3 is formed in a side wall of the cylinder 1. A hole portion 6 is formed in the bottom wall of the cylinder 1, and one end of a suction tube 5 is connected thereto. A communicating hole 7 is formed in the piston 2. The piston 2 is urged upward by a coil spring 8. In the non-suction (ready) mode, the piston 2 abuts against an annular stopper 10, as shown in FIG. 1. The opening 4 is not aligned with the communicating hole 7, so that a suction channel 11 is closed. However, as shown in FIG. 2, when the operator closes a leakage hole 12 while pressing the piston 2, that is, when the suction mode is initiated, the opening 4 is aligned with the communicating hole 7, thereby opening the suction channel 11.
In order to guarantee the above selection operation, there must be provided a regulating means which does not allow rotation of the piston 2 but only allows movement of the piston 2 along the axial direction of the cylinder 1. In the conventional mechanism, an elongated groove 14 is formed in the outer surface of the piston 2 along the axial direction thereof, while a pin 15 for preventing rotation of the piston 2 is fixed at a portion of the cylinder 1 such that the pin 15 can be engaged with the elongated groove 14.
In the conventional mechanism having the above configuration, because a pin 15 is required, the number of components increases. Furthermore, the regulating means described above is required, resulting in complex construction and high cost. When the piston 2 is mounted in the cylinder 1, the pin 15 must be engaged with the elongated groove 14. Therefore, the mounting operation, which must be performed every time the mechanism is cleaned and sterilized after use, is very cumbersome and time consuming.